Measuring Compressive Strength Characteristics of Soil-Dobak-Glue Mixtures over Curing Time

The building materials used by mankind in the past, such as stone, soil, and wood, have been environment-friendly. However, the various building materials invented over time with the development of the industrial age pose problems such as environmental hormone generation and waste generation/disposal. To overcome these problems, building materials based on soil, a traditional building material, are being developed by researchers. However, the improvement in soil’s structural characteristics is insufficient as it excessively emphasizes efficacy and function only. In this study, lime and Dobak-glue were mixed with soil to solve the structural problems and improve the strength of soil, and water content and change in strength in accordance with curing time were tested. In order to understand the change in strength, a compaction test was performed by preparing a standard specimen based on the optimum water content and maximum dry density. The lime mix required optimum water content and quantity of lime equal to 3% of soil weight, while the Dobak-glue mix was prepared by soil mixing in the same weight ratio as optimum water content. Changes in water content and compressive strength were measured over curing time of 3, 7, and 28 days. Three specimens, lime mixed specimen, Dobak-glue mixed specimen, and standard specimen, were prepared, and their water content and compressive strength values were averaged. Although the change in water content according to the curing period differed depending on the material mixed with soil, there was no significant difference between 7.12% and 2.82% after 7 days. As for the change in compressive strength, the initial compressive strength in lime mixed specimen was excellent, but the Dobak-glue mixed specimen displayed the greatest strength after 7 days. To conclude, Dobak-glue is an eco-friendly material, and it can be very useful in compensating for the structural shortcomings of soil.

What Makes Cow-Dung Stabilised Earthen Block Water-Resistant

The water-resistance of cow-dung has made it a widely used stabiliser in traditional earthen structures in several Asian and African countries. Multiple studies have shown an improvement in water-resistance with the addition of cow-dung, but none provides insight into this behaviour. The present study investigates the water-resistance behaviour of cow-dung stabilised earthen blocks through an extensive experimental programme to identify and characterise the components of cow-dung responsible for its water-resistance. Fresh cow-dung was collected and separated into fibres (>63 μm), medium-sized microbial aggregates (1-63 μm) and small-sized microbial aggregates (0.5-7 μm). Each component was mixed with soil and samples were prepared at different water contents (optimum water content corresponding to the highest dry density and water content higher than optimum) and compacted with 2.5 MPa force to prepare compressed blocks. The water-resistance of these blocks was evaluated through the immersion and modified drip/rain test. It was found that the small-sized microbial aggregates are almost entirely responsible for water-resistance behaviour of cow-dung stabilised earthen blocks. Small-sized microbial aggregates were further characterised by gas chromatography, mercury intrusion porosimetry, N2- BET surface area, zeta potential measurement and electron microscopy. The results indicate that the small-sized microbial aggregates are composed of clay-sized negatively charged particles that are rich in fatty acids. The hydrophobicity of these particles is hypothesised to be responsible for water-resistance behaviour. These insights are further used to produce stabilised blocks that performed at least 30 times better than the unstabilised blocks in both water-resistance tests. The study concludes with practical recommendations for the use of wet cow-dung over dry cow-dung and a reduction of fibre content to increase the water-resistance of earthen blocks.

Strengthening Of Soft Soil Using Caboxymethyl Cellelouse Biopolymer

The application of appropriate chemicals is a widely used strategy for soil stabilization. The drive of this study is to determine the possibility of using the biopolymer carboxymethyl cellulose as an environmentally acceptable soil stabilizer. In this work, Atterberge limits tests, specific gravity, compaction, and consolidation tests were used to determine the engineering parameters of soils treated with varying amounts of biopolymer. Additionally, changes in the morphological properties of the soft soils were evaluated using scanning electron microscopy (SEM). It was estimated that as the soil’s biopolymer content increases, the specific gravity drops down, though the optimum water content (OMC) is extended. The outcomes showed diverse effects on Atterberg’s limits by cumulative the liquid limit(LL) and plasticity index (PI) though decreasing the plastic limit as the bio-polymer content increases. By the addition in polymer gratified, the combination boundaries (Solidity index Cc and recompression index Cr) decline.

The effect of water content and carbon source addition on lipase production from Aspergillus aculeatus Ms.11 using spent coffee ground

Lipase is one of the industrially important enzymes, however, the production needs costly substrate. To overcome the problem, we developed an effective medium formulation to produce lipase from indigenous lipolytic mould Aspergillus aculeatus Ms.11 using spent coffee ground. We observed the effect of additional glucose and olive oil, and the influence of water content on lipase production. The experiments were done using the Solid-State Fermentation (SSF) method for 7 days. The results show that optimum lipase production on substrates with additional glucose and olive oil observed on day 4 with lipase activity of 16.296 U/mL and lipase productivity of 150.32 U/g/day. The optimum water content from the results is 50%. The highest lipase activity obtained using the water content is 291.80 U/mL, while the highest lipase productivity is 106.32 U/g/day. The results showed that water content as well as the addition of glucose and olive oil, affects lipase productivity of Aspergillus aculeatus Ms.11 on spent coffee ground. Further studies to optimise the production condition are suggested.

Evaluation of the influence of compaction energy on the resilient behavior of lateritic soil in the field and laboratory

This article presents the study of the resilient behavior of three soil horizons from a deposit of lateritic soil employed in a pavement structure in Rio Grande do Sul, Brazil. The use of lateritic soils in pavement layers is a common practice in Brazil and due to its peculiarities, its behavior must be investigated. The methodology consisted of physical and chemical characterization and resilient modulus determination. Samples from the three horizons, compacted at standard, intermediate and modified energy, were analyzed. In addition, undisturbed samples extracted from the interior and top layer of the embankment were submitted to repeated load triaxial tests for resilient modulus determination. The results indicated that the soil exhibit good behavior for pavement subgrade applications, perhaps as subbase or base course layers. The compound and universal models yielded the best correlation coefficients. Furthermore, the results showed that as the compaction energy increased, the resilient modulus also increased, as long as they are within the optimum water content and compaction degree limit. However, when subjected to immersion in water for four days, the resilient behavior decreased about 73% in relation to unsaturated samples.

Role of Fly Ash on Strength Properties of Rejuvenated Soil Cement for Pavement Materials

Stabilization with cement is the most commonly used technique for the improvement of soil physical, mechanical, and engineering properties. This research reported on the properties of the rejuvenation for recycled soil cement with incorporation of fly ash (FA). The study showed that the specific gravity of Rejuvenated Soil Cement (RSC) decreased with increasing FA. The free swell ratio and linear shrinkage of RSC were significantly decreased with the increase in FA. The maximum dry unit weight of RSC increased with increasing FA up to the optimum FA content of 20 – 25 %. The optimum water content in compaction was relatively constant with the increase in FA. Particularly, the strength improvement in active zone of FA-RSC was influenced by several factors viz., compaction, packing, rehydration, and pozzolanic reaction. As a result, the unconfined compressive strength (UCS) of RSC increased with increase in FA and curing time. This research clearly showed that the rejuvenation of soil-cement with FA as additive was successful. It was also shown that the normalized UCSs of RSC at various curing times could be used to predict the UCSs at 7 and 28 days.

Pemanfaatan Limbah Penambangan Bukit Kapur Untuk Stabilisasi Tanah Lempung ( Clay )

Soil stabilization by adding new materials is one of the alternatives to soil repair that can improve the properties of the soil, namely by mixing new materials and soil that is then compacted. Waste left over limestone hill mining,among others in the form of materials with various sizes of granules. This study aims to review the effect of the addition of limestone hill mining waste material on the density and value of the California Bearing Ratio (CBR) of clay soil. Tests conducted only on a laboratory scale with variations in the increase in limestone hill mining waste levels are 0%, 5%, 10%, and 15% to the total weight of the mixture. Laboratory CBR testing is performed under optimum water content conditions. The results showed that the stabilization of soft soils using limestone hill mining waste, can increase the density and value of soil CBR. The most optimal level of use of limestone hill mining waste and which provides the highest CBR value is for the addition of 5%of limestone hill mining waste with a CBR value of 26.5%.

Effect of Expanded Polystyrene Particle Size on Engineering Properties of Clayey Soil

The particle size of expanded polystyrene (EPS) has an effect on engineering properties of EPS-clay blends. However, the effect of differences between EPS particle size groups subdivided within 1–3 mm on engineering properties is usually ignored. In this study, different particle sizes of EPS pellets have been considered to separately investigate the effect on the optimum water content (OWC), maximum dry density (MDD), unconfined compressive strength (UCS), ductility, coefficient of permeability, and compression index of EPS-clay blends. Results show that the MDD, ductility, hydraulic conductivity, and compression index of EPS-clay blends do not increase with the increase in the EPS particle size in the range of 0.3–3 mm, while the OWC and UCS do not decrease. For a given EPS content, among samples with the EPS particle size of 0.3–1 mm, 1-2 mm, and 2-3 mm, the MDD and UCS of EPS-clay blends with 1-2 mm in EPS particle size are the largest, while the OWC, ductility, coefficient of permeability, and compression index are the smallest. Microstructure analyses reveal that, for samples with the EPS particle size of 1-2 mm, the pore volume is lower and the microstructure is denser, which are the main reasons why the EPS particle size can influence engineering properties of EPS-clay blends.

Estimation of Optimum Moisture Content and Maximum Dry Unit Weight of Fine-Grained Soils using Numerical Methods

Soil compaction is one of the basic engineering techniques, which is carried out to guarantee the stability of soils dependent on specified strength. Nonetheless, in large-scale construction projects, the estimation of compaction features required tremendous effort and time that can be saved utilizing empirical relationships at the initial phases. It becomes critical to develop models to predict the compaction features, namely the maximum dry unit weight (γdmax) and optimum water content (WOP). This article attempts to develop models to predict the γdmax and WOP of fine-grained clay soils. Geotechnical tests such as grain size distribution, Atterberg limits, specific gravity, and proctor compaction tests are performed to assess soil samples' physical and hyro-mechanical characteristics. Multivariate analysis is conducted using MINITAB 18 software to develop the predictive models. The validation process of developed models includes the determination coefficient, probability value (p-value), comparison of the predicted values with experimental values, comparison of the models proposed in this study with other existing models found in the recent literature, and employing a different soil data set. The predicted values obtained from the models proposed in this research project are more accurate than other models developed recently. The proposed models estimate the compaction features of fine-grained clay soils with acceptable precision. HIGHLIGHTS Soil compaction is one of the basic engineering techniques perform to guarantee the stability of soils dependent on specified strength In large-scale construction projects, the estimation of compaction parameters required tremendous effort and time that can be saved utilizing empirical relationships at the initial phases This study has developed semi-empirical models to predict the compaction parameters (maximum dry unit weight and optimum water content) of fine-grained soils GRAPHICAL ABSTRACT